Marva Whitney, James Brown’s principal backup singer and onstage foil during the soul star’s late-’60s heyday, died Dec. 23. She was 68.Whitney’s passing was announced on her official Facebook page. No cause of death was revealed, but England’s New Musical Express reported she died from pneumonia complications. She had suffered a stroke in 2009 while performing in Australia. Born Marva Ann Manning in Kansas City, Kansas, Whitney performed with her family’s Manning Gospel Singers and R&B act Tommy Gadson & the Derbys before becoming a mainstay of Brown’s live show from 1967-69. She told Brown’s biographer RJ Smith that the vocalist reshaped her style: “I learned to do…what Mr. Brown called ‘on the one.’ See, I didn’t sing on the one, and that doesn’t come overnight.” She accompanied Brown’s crack band on his 1968 tour of Asia and Southeast Asia, playing USO dates for servicemen in Vietnam. She said she made the potentially hazardous trip because, in her words, “The soldiers needed to see a sister who wasn’t an Oreo cookie.” Backed by the Brown band and produced by Soul Brother No. 1, Whitney cut several singles for King Records. The biggest of them, “It’s My Thing (You Can’t Tell Me Who to Sock It To”), an answer to the Isley Brothers’ hit “It’s Your Thing,” reached No. 19 on the U.S. R&B chart in 1969. It lent its name to the singer’s album of that year. After Whitney quit Brown’s group, she recorded without success for Excello’s Nashboro imprint and the Isleys’ T-Neck Records. However, her best-known work lived on in samples: Her Brown-produced tracks “It’s My Thing” and “Unwind Yourself” were sampled by the likes of DJ Kool, Sway and, just last year, chart-topping rapper Mac Miller. Whitney’s 2006 collaboration with Japanese funk band Osaka Monorail led to a new full-length album, “I Am What I Am,” and tours of Japan and Europe. She outlived her former mentor and boss by six years: James Brown died on Christmas 2006.